Hydrocarbon feeds derived from various oil and gas processing operations such as, for example, various bitumen-derived hydrocarbon fractions often contain impurities harmful to the efficient operation of downstream processes, and affect the quality of the final hydrocarbon product. Such impurities include salts commonly found in hydrocarbon feeds such as, for example, sodium chloride, magnesium chloride and calcium chloride. These salts are unstable at elevated temperatures, and if allowed to remain in the hydrocarbon feeds throughout the various stages of processing, they will dissociate and form corrosive compounds (e.g., hydrochloric acid), which contribute to corrosion of equipment such as piping and instrumentation for instance. In addition to sodium, magnesium and calcium salts, other metal salts including potassium, nickel, vanadium, copper, iron and zinc may also be found in various hydrocarbon feeds and contribute to fouling of equipment, coking, catalyst poisoning and end product degradation.
Dehydrated and salty hydrocarbon feeds may arise when hydrocarbon feeds, initially containing water with dissolved salts, are substantially dehydrated by removal of bulk water and removal of the water as water vapour for example. Hydrocarbon feeds containing water are also called emulsions or more precisely water-in-hydrocarbon emulsions. The mass percent of water in such hydrocarbon emulsions can range from about 0.01 wt. % to about 50 wt. %. When water is substantially removed from such emulsions, as vapour for example, dissolved salts which cannot be vaporized with the water, and thereby removed, will remain as very fine solids dispersed within the hydrocarbon material resulting in the hydrocarbon material having a dispersed salt content.
A variety of approaches have been proposed for desalting dehydrated and salty hydrocarbon feeds. For example, one conventional approach involves mixing water with the dehydrated and salty hydrocarbon feeds so that water may solubilize the salts dispersed in the hydrocarbon material of the feed and thereby desalt the hydrocarbon feed. Addition of water, however, results in emulsion formation, which is often challenging to resolve and requires various chemical treatments or other methods such as, for example, the use of electrical field to effect emulsion breaking and phase separation. Furthermore, the salts attempted to be removed with water may continue to remain with the hydrocarbon feed at relatively high levels due to poor contact with the added water, and may cause problems in downstream operations.
Therefore, there is a need in the industry for processing dehydrated and salty hydrocarbon feeds to effect desalting to obtain feeds suitable for downstream processing operations including upgrading.